Hydroxyurea differentially modulates activator and repressors of γ-globin gene in erythroblasts of responsive and non-responsive patients with sickle cell disease in correlation with Index of Hydroxyurea Responsiveness
Xingguo Zhu,
Tianxiang Hu,
Meng Hsuan Ho,
Yongchao Wang,
Miao Yu,
Niren Patel,
Wenhu Pi,
Jeong-Hyeon Choi,
Hongyan Xu,
Vadivel Ganapathy,
Ferdane Kutlar,
Abdullah Kutlar,
Dorothy Tuan
Affiliations
Xingguo Zhu
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA
Tianxiang Hu
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA
Meng Hsuan Ho
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA;School of Dentistry, Meharry Medical College, Nashville, TN, USA
Yongchao Wang
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA;Department of Pharmacology and Nutritional Sciences, University of Kentucky, Lexington, KY, USA
Miao Yu
Georgia Cancer Research Center, Augusta University, GA, USA
Niren Patel
Division of Hematology/Oncology, Augusta University, GA, USA
Wenhu Pi
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA;Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN, USA
Jeong-Hyeon Choi
Georgia Cancer Research Center, Augusta University, GA, USA;Department of Biostatistics, Augusta University, GA, USA
Hongyan Xu
Department of Biostatistics, Augusta University, GA, USA
Vadivel Ganapathy
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA;Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, USA
Ferdane Kutlar
Division of Hematology/Oncology, Augusta University, GA, USA
Abdullah Kutlar
Division of Hematology/Oncology, Augusta University, GA, USA
Dorothy Tuan
Department of Biochemistry and Molecular Biology, Augusta University, GA, USA
Hydroxyurea (HU), the first of two drugs approved by the US Food and Drug Administration for treating patients with sickle cell disease (SCD), produces anti-sickling effect by re-activating fetal γ-globin gene to enhance production of fetal hemoglobin. However, approximately 30% of the patients do not respond to HU therapy. The molecular basis of non-responsiveness to HU is not clearly understood. To address this question, we examined HU-induced changes in the RNA and protein levels of transcription factors NF-Y, GATA-1, -2, BCL11A, TR4, MYB and NF-E4 that assemble the γ-globin promoter complex and regulate transcription of γ-globin gene. In erythroblasts cultured from peripheral blood CD34+ cells of patients with SCD, we found that HU-induced changes in the protein but not the RNA levels of activator GATA-2 and repressors GATA-1, BCL11A and TR4 correlated with HU-induced changes in fetal hemoglobin (HbF) levels in the peripheral blood of HU high and low responders. However, HU did not significantly induce changes in the protein or RNA levels of activators NF-Y and NF-E4. Based on HU-induced changes in the protein levels of GATA-2, -1 and BCL11A, we calculated an Index of Hydroxyurea Responsiveness (IndexHU-3). Compared to the HU-induced fold changes in the individual transcription factor protein levels, the numerical values of IndexHU-3 statistically correlated best with the HU-induced peripheral blood HbF levels of the patients. Thus, IndexHU-3 can serve as an appropriate indicator for inherent HU responsiveness of patients with SCD.
